Data Processing In A Hybrid Computing Environment

ABSTRACT

Data processing in a hybrid computing environment that includes a host computer and an accelerator, the host and the accelerator adapted to one another for data communications by a system level message passing module and a plurality data communications fabrics of at least two different fabric types, the data processing including: monitoring data communications performance for a plurality of data communications modes; receiving, from an application program on the host computer, a request to transmit data according to a data communications mode from the host computer to the accelerator; determining, in dependence upon the monitored performance, whether to transmit the data according to the requested data communications mode; and if the data is not to be transmitted according to the requested data communications mode: selecting, in dependence upon the monitored performance, another data communications mode for transmitting the data and transmitting the data according to the selected data communications mode.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of the invention is data processing, or, more specifically,methods, apparatus, and products for data processing in a hybridcomputing environment.

2. Description of Related Art

The development of the EDVAC computer system of 1948 is often cited asthe beginning of the computer era. Since that time, computer systemshave evolved into extremely complicated devices. Today's computers aremuch more sophisticated than early systems such as the EDVAC. Computersystems typically include a combination of hardware and softwarecomponents, application programs, operating systems, processors, buses,memory, input/output (‘I/O’) devices, and so on. As advances insemiconductor processing and computer architecture push the performanceof the computer higher and higher, more sophisticated computer softwarehas evolved to take advantage of the higher performance of the hardware,resulting in computer systems today that are much more powerful thanjust a few years ago.

Computer systems today have advanced such that some computingenvironments now include core components of different architectureswhich operate together to complete data processing tasks. Such computingenvironments are described in this specification as ‘hybrid’environments, denoting that such environments include host computers andaccelerators having different architectures. Although hybrid computingenvironments are more computationally powerful and efficient in dataprocessing than many non-hybrid computing environments, such hybridcomputing environments still present substantial challenges to thescience of automated computing machinery.

SUMMARY OF THE INVENTION

Methods, apparatus, and products for data processing in a hybridcomputing environment, the hybrid computing environments including ahost computer having a host computer architecture and an acceleratorhaving an accelerator architecture, the accelerator architectureoptimized, with respect to the host computer architecture, for speed ofexecution of a particular class of computing functions, the hostcomputer and the accelerator adapted to one another for datacommunications by a system level message passing module, the hostcomputer and the accelerator adapted to one another for datacommunications by two or more data communications fabrics of at leasttwo different fabric types.

Data processing in such a hybrid computing environment includes:monitoring, by the system level message passing module, datacommunications performance for a plurality of data communications modesbetween the host computer and the accelerator; receiving, by the systemlevel message passing module from an application program on the hostcomputer, a request to transmit data according to a data communicationsmode from the host computer to the accelerator; determining, by thesystem level message passing module, in dependence upon the monitoredperformance whether to transmit the data according to the requested datacommunications mode; and if the data is not to be transmitted accordingto the requested data communications mode: selecting, by the systemlevel message passing module, in dependence upon the monitoredperformance another data communications mode for transmitting the dataand transmitting the data by the system level message passing moduleaccording to the selected data communications mode.

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescriptions of exemplary embodiments of the invention as illustrated inthe accompanying drawings wherein like reference numbers generallyrepresent like parts of exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 sets forth a diagram of an example hybrid computing environmentuseful for data processing according to embodiments of the presentinvention.

FIG. 2 sets forth a block diagram of an exemplary hybrid computingenvironment according to embodiments of the present invention.

FIG. 3 sets forth a block diagram of a further exemplary hybridcomputing environment according to embodiments of the present invention.

FIG. 4 sets forth a block diagram of a further exemplary hybridcomputing environment according to embodiments of the present invention.

FIG. 5 sets forth a flow chart illustrating an exemplary method for dataprocessing in a hybrid computing environment according to embodiments ofthe present invention.

FIG. 6 sets forth a flow chart illustrating a further exemplary methodfor data processing in a hybrid computing environment according toembodiments of the present invention.

FIG. 7 sets forth a flow chart illustrating a further exemplary methodfor data processing in a hybrid computing environment according toembodiments of the present invention.

FIG. 8 sets forth a flow chart illustrating a further exemplary methodfor data processing in a hybrid computing environment according toembodiments of the present invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary methods, apparatus, and products for data processing in ahybrid computing environment according to embodiments of the presentinvention are described with reference to the accompanying drawings,beginning with FIG. 1. FIG. 1 sets forth a diagram of an example hybridcomputing environment (100) useful for data processing according toembodiments of the present invention. A ‘hybrid computing environment,’as the term is used in this specification, is a computing environment inthat it includes computer processors operatively coupled to computermemory so as to implement data processing in the form of execution ofcomputer program instructions stored in the memory and executed on theprocessors. In addition, the hybrid computing environment (100) in theexample of FIG. 1 includes at least one host computer having a hostarchitecture that operates in cooperation with an accelerator having anaccelerator architecture where the host architecture and acceleratorarchitecture are different architectures. The host and acceleratorarchitectures in this example are characterized by architecturalregisters, registers that are accessible by computer programinstructions that execute on each architecture, registers such as, forexample, an instruction register, a program counter, memory indexregisters, stack pointers, and the like. That is, the number, type,structure, and relations among the architectural registers of the twoarchitectures are different, so different that computer programinstructions compiled for execution on the host computer of a hybridcomputing environment typically cannot be executed natively by anyassociated accelerator of the hybrid computing environment.

Examples of hybrid computing environments include a data processingsystem that in turn includes one or more host computers, each having anx86 processor, and accelerators whose architectural registers implementthe PowerPC instruction set. Computer program instructions compiled forexecution on the x86 processors in the host computers cannot be executednatively by the PowerPC processors in the accelerators. Readers willrecognize in addition that some of the example hybrid computingenvironments described in this specification are based upon the LosAlamos National Laboratory (‘LANL’) supercomputer architecture developedin the LANL Roadrunner project (named for the state bird of New Mexico),the supercomputer architecture that famously first generated a‘petaflop,’ a million billion floating point operations per second. TheLANL supercomputer architecture includes many host computers withdual-core AMD Opteron processors coupled to many accelerators with IBMCell processors, the Opteron processors and the Cell processors havingdifferent architectures.

The example hybrid computing environment (100) of FIG. 1 includes aplurality of compute nodes (102), I/O nodes (108), and a service node(112). The compute nodes (102) are coupled through network (101) fordata communications with one another and with the I/O nodes (108) andthe service node (112). The data communications network (101) may beimplemented as an Ethernet, Internet Protocol (‘IP’), PCIe, Infiniband,Fibre Channel, or other network as will occur to readers of skill in theart.

In the example hybrid computing environment (100) of FIG. 1, the computenodes carry out principal user-level computer program execution,accepting administrative services, such as initial program loads and thelike, from the service application (124) executing on the service node(112) and gaining access to data storage (116) and I/O functionality(118, 120) through the I/O nodes (108). In the example of FIG. 1, theI/O nodes (108) are connected for data communications to I/O devices(116, 118, 120) through a local area network (‘LAN’) (114) implementedusing high-speed Ethernet or a data communications fabric of anotherfabric type as will occur to those of skill in the art. I/O devices inthe example hybrid computing environment (100) of FIG. 1 includenon-volatile memory for the computing environment in the form of datastorage device (116), an output device for the hybrid computingenvironment in the form of printer (118), and a user (126) I/O device inthe form of computer terminal (120) that executes a service applicationinterface (122) that provides to a user an interface for configuringcompute nodes in the hybrid computing environment and initiatingexecution by the compute nodes of principal user-level computer programinstructions.

In the example of FIG. 1, each compute node includes a host computer(110) having a host computer architecture and one or more accelerators(104) having an accelerator architecture. A host computer (110) is a‘host’ in the sense that it is the host computer that carries outinterface functions between a compute node and other components of thehybrid computing environment external to any particular compute node.That is, it is the host computer that executes initial boot procedures,power on self tests, basic I/O functions, accepts user-level programloads from service nodes, and so on. An accelerator (104) is an‘accelerator’ in that each accelerator has an accelerator architecturethat is optimized, with respect to the host computer architecture, forspeed of execution of a particular class of computing functions. Suchaccelerated computing functions include, for example, vector processing,floating point operations, and others as will occur to those of skill inthe art.

Because each of the compute nodes in the example of FIG. 1 includes ahost computer and an accelerator, readers of skill in the art willrecognize that each compute node represents a smaller, separate hybridcomputing environment within the larger hybrid computing environment(100) of FIG. 1. That is, not only may the combination of the computenodes (102) form a hybrid computing environment (100), but it is alsothe case that each individual compute node may also be viewed as aseparate, smaller hybrid computing environment. The hybrid computingenvironment (100) in the example of FIG. 1 then, may be viewed ascomposed of nine separate, smaller hybrid computing environments, onefor each compute node, which taken together form the hybrid computingenvironment (100) of FIG. 1.

Within each compute node (102) of FIG. 1, a host computer (110) and oneor more accelerators (104) are adapted to one another for datacommunications by a system level message passing module (‘SLMPM’) (146)and by two or more data communications fabrics (106, 107) of at leasttwo different fabric types. An SLMPM (146) is a module or library ofcomputer program instructions that exposes an application programminginterface (‘API’) to user-level applications for carrying outmessage-based data communications between the host computer (110) andthe accelerator (104). Examples of message-based data communicationslibraries that may be improved for use as an SLMPM according toembodiments of the present invention include:

-   -   the Message Passing Interface or ‘MPI,’ an industry standard        interface in two versions, first presented at Supercomputing        1994, not sanctioned by any major standards body,    -   the Data Communication and Synchronization interface (‘DACS’) of        the LANL supercomputer,    -   the POSIX Threads library (‘Pthreads’), an IEEE standard for        distributed, multithreaded processing,    -   the Open Multi-Processing interface (‘OpenMP’), an        industry-sanctioned specification for parallel programming, and    -   other libraries that will occur to those of skill in the art.

A data communications fabric (106, 107) is a configuration of datacommunications hardware and software that implements a datacommunications coupling between a host computer and an accelerator.Examples of data communications fabric types include PeripheralComponent Interconnect (‘PCI’), PCI express (‘PCIe’), Ethernet,Infiniband, Fibre Channel, Small Computer System Interface (‘SCSI’),External Serial Advanced Technology Attachment (‘eSATA’), UniversalSerial Bus (‘USB’), and so on as will occur to those of skill in theart.

The arrangement of compute nodes, data communications fabrics, networks,I/O devices, service nodes, I/O nodes, and so on, making up the hybridcomputing environment (100) as illustrated in FIG. 1 are for explanationonly, not for limitation of the present invention. Hybrid computingenvironments capable of data processing according to embodiments of thepresent invention may include additional nodes, networks, devices, andarchitectures, not shown in FIG. 1, as will occur to those of skill inthe art. Although the hybrid computing environment (100) in the exampleof FIG. 1 includes only nine compute nodes (102), readers will note thathybrid computing environments according to embodiments of the presentinvention may include any number of compute nodes. The LANLsupercomputer, taken as an example of a hybrid computing environmentwith multiple compute nodes, contains as of this writing more than12,000 compute nodes. Networks and data communications fabrics in suchhybrid computing environments may support many data communicationsprotocols including for example TCP (Transmission Control Protocol), IP(Internet Protocol), and others as will occur to those of skill in theart. Various embodiments of the present invention may be implemented ona variety of hardware platforms in addition to those illustrated in FIG.1.

For further explanation, FIG. 2 sets forth a block diagram of anexemplary hybrid computing environment (100) useful for data processingaccording to embodiments of the present invention. The hybrid computingenvironment (100) of FIG. 2 includes four compute nodes. Similar to thecompute nodes of FIG. 1, each of the compute nodes in the example ofFIG. 2 may represent a small, separate hybrid computing environmentwhich taken together make up a larger hybrid computing environment. Onecompute node (103) in the example of FIG. 2 is illustrated in anexpanded view to aid a more detailed explanation of such a hybridcomputing environment (100). As shown in the expanded view of computenode (103), each of the compute nodes (102, 103) in the example of FIG.2 includes a host computer (110). The host computer (110) includes acomputer processor (152) operatively coupled to computer memory, RandomAccess Memory (‘RAM’) (142), through a high speed memory bus (153). Theprocessor (152) in each host computer (110) has a set of architecturalregisters (154) that defines the host computer architecture.

Each of the compute nodes also includes one or more accelerators (104,105). Each accelerator (104, 105) includes a computer processor (148)operatively coupled to RAM (140) through a high speed memory bus (151).Stored in RAM (140,142) of the host computer and the accelerators (104,105) is an operating system (145). Operating systems useful in hostcomputers and accelerators of hybrid computing environments according toembodiments of the present invention include UNIX™, Linux™, MicrosoftXP™, Microsoft Vista™, Microsoft NT™, AIX™, IBM's i5/OS™, and others aswill occur to those of skill in the art. There is no requirement thatthe operating system in the host computers should be the same operatingsystem used on the accelerators.

The processor (148) of each accelerator (104, 105) has a set ofarchitectural registers (150) that defines the accelerator architecture.The architectural registers (150) of the processor (148) of eachaccelerator are different from the architectural registers (154) of theprocessor (152) in the host computer (110). With differingarchitectures, it would be uncommon, although possible, for a hostcomputer and an accelerator to support the same instruction sets. Assuch, computer program instructions compiled for execution on theprocessor (148) of an accelerator (104) generally would not be expectedto execute natively on the processor (152) of the host computer (110)and vice versa. Moreover, because of the typical differences in hardwarearchitectures between host processors and accelerators, computer programinstructions compiled for execution on the processor (152) of a hostcomputer (110) generally would not be expected to execute natively onthe processor (148) of an accelerator (104) even if the acceleratorsupported the instruction set of the host. The accelerator architecturein example of FIG. 2 is optimized, with respect to the host computerarchitecture, for speed of execution of a particular class of computingfunctions. That is, for the function or functions for which theaccelerator is optimized, execution of those functions will proceedfaster on the accelerator than if they were executed on the processor ofthe host computer.

In the example of FIG. 2, the host computer (110) and the accelerators(104, 105) are adapted to one another for data communications by asystem level message passing module (‘SLMPM’) (146) and two datacommunications fabrics (128, 130) of at least two different fabrictypes. In this example, to support message-based data communicationsbetween the host computer (110) and the accelerator (104), both the hostcomputer (110) and the accelerator (104) have an SLMPM (146) so thatmessage-based communications can both originate and be received on bothsides of any coupling for data communications. Also in the example ofFIG. 2, the host computer (110) and the accelerators (104, 105) areadapted to one another for data communications by a PCIe fabric (130)through PCIe communications adapters (160) and an Ethernet fabric (128)through Ethernet communications adapters (161). The use of PCIe andEthernet is for explanation, not for limitation of the invention.Readers of skill in the art will immediately recognize that hybridcomputing environments according to embodiments of the present inventionmay include fabrics of other fabric types such as, for example, PCI,Infiniband, Fibre Channel, SCSI, eSATA, USB, and so on.

The SLMPM (146) in this example operates generally for data processingin a hybrid computing environment (100) according to embodiments of thepresent invention by monitoring data communications performance for aplurality of data communications modes between the host computer (110)and the accelerators (104, 105), receiving a request (168) to transmitdata according to a data communications mode from the host computer toan accelerator, determining whether to transmit the data according tothe requested data communications mode, and if the data is not to betransmitted according to the requested data communications mode:selecting another data communications mode and transmitting the dataaccording to the selected data communications mode. In the example ofFIG. 2, the monitored performance is illustrated as monitoredperformance data (174) stored by the SLMPM (146) in RAM (142) of thehost computer (110) during operation of the compute node (103).

A data communications mode specifies a data communications fabric type,a data communications link, and a data communications protocol (178). Adata communications link (156) is data communications connection betweena host computer and an accelerator. In the example of FIG. 2, a link(156) between the host computer (110) and the accelerator (104) mayinclude the PCIe connection (138) or the Ethernet connection (131, 132)through the Ethernet network (106). A link (156) between the hostcomputer (110) and the accelerator (105) in the example of FIG. 2, mayinclude the PCIe connection (136) or the Ethernet connection (131, 134)through the Ethernet network (106). Although only one link for eachfabric type is illustrated between the host computer and the acceleratorin the example of FIG. 2, readers of skill in the art will immediatelyrecognize that there may any number of links for each fabric type.

A data communications protocol is a set of standard rules for datarepresentation, signaling, authentication and error detection requiredto send information from a host computer (110) to an accelerator (104).In the example of FIG. 2, the SLMPM (146) may select one of severalprotocols (178) for data communications between the host computer (110)and the accelerator. Examples of such protocols (178) include sharedmemory transfers (‘SMT’) (180) executed with a send and receiveoperations (181), and direct memory access (‘DMA’) (182) executed withPUT and GET operations (183).

Shared memory transfer is a data communications protocol for passingdata between a host computer and an accelerator into shared memory space(158) allocated for such a purpose such that only one instance of thedata resides in memory at any time. Consider the following as an exampleshared memory transfer between the host computer (110) and theaccelerator (104) of FIG. 2. An application (166) requests (168) atransmission of data (176) from the host computer (110) to theaccelerator (104) in accordance with the SMT (180) protocol. Such arequest (168) may include a memory address allocated for such sharedmemory. In this example, the shared memory segment (158) is illustratedin a memory location on the accelerator (104), but readers willrecognize that shared memory segments may be located on the accelerator(104), on the host computer (110), on both the host computer and theaccelerator, or even off the local compute node (103) entirely—so longas the segment is accessible as needed by the host and the accelerator.To carry out a shared memory transfer, the SLMPM (146) on the hostcomputer (110) establishes a data communications connection with theSLMPM (146) executing on the accelerator (104) by a handshakingprocedure similar to that in the TCP protocol. The SLMPM (146) thencreates a message (170) that includes a header and a payload data andinserts the message into a message transmit queue for a particular linkof a particular fabric. In creating the message, the SLMPM inserts, inthe header of the message, an identification of the accelerator and anidentification of a process executing on the accelerator. The SLMPM alsoinserts the memory address from the request (168) into the message,either in the header or as part of the payload data. The SLMPM alsoinserts the data (176) to be transmitted in the message (170) as part ofthe message payload data. The message is then transmitted by acommunications adapter (160, 161) across a fabric (128, 130) to theSLMPM executing on the accelerator (104) where the SLMPM stores thepayload data, the data (176) that was transmitted, in shared memoryspace (158) in RAM (140) in accordance with the memory address in themessage.

Direct memory access (‘DMA’) is a data communications protocol forpassing data between a host computer and an accelerator with reducedoperational burden on the computer processor (152). A DMA transferessentially effects a copy of a block of memory from one location toanother, typically from a host computer to an accelerator or vice versa.Either or both a host computer and accelerator may include DMA engine,an aggregation of computer hardware and software for direct memoryaccess. Direct memory access includes reading and writing to memory ofaccelerators and host computers with reduced operational burden on theirprocessors. A DMA engine of an accelerator, for example, may write to orread from memory allocated for DMA purposes, while the processor of theaccelerator executes computer program instructions, or otherwisecontinues to operate. That is, a computer processor may issue aninstruction to execute a DMA transfer, but the DMA engine, not theprocessor, carries out the transfer.

In the example of FIG. 2, only the accelerator (104) includes a DMAengine (184) while the host computer does not. In this embodiment theprocessor (152) on the host computer initiates a DMA transfer of datafrom the host to the accelerator by sending a message according to theSMT protocol to the accelerator, instructing the accelerator to performa remote ‘GET’ operation. The configuration illustrated in the exampleof FIG. 2 in which the accelerator (104) is the only device containing aDMA engine is for explanation only, not for limitation. Readers of skillin the art will immediately recognize that in many embodiments, both ahost computer and an accelerator may include a DMA engine, while in yetother embodiments only a host computer includes a DMA engine.

To implement a DMA protocol in the hybrid computing environment of FIG.2 some memory region is allocated for access by the DMA engine.Allocating such memory may be carried out independently from otheraccelerators or host computers, or may be initiated by and completed incooperation with another accelerator or host computer. Shared memoryregions, allocated according to the SMA protocol, for example, may bememory regions made available to a DMA engine. That is, the initialsetup and implementation of DMA data communications in the hybridcomputing environment (100) of FIG. 2 may be carried out, at least inpart, through shared memory transfers or another out-of-band datacommunications protocol, out-of-band with respect to a DMA engine.Allocation of memory to implement DMA transfers is relatively high inlatency, but once allocated, the DMA protocol provides for highbandwidth data communications that requires less processor utilizationthan many other data communications protocols.

A direct ‘PUT’ operation is a mode of transmitting data from a DMAengine on an origin device to a DMA engine on a target device. A direct‘PUT’ operation allows data to be transmitted and stored on the targetdevice with little involvement from the target device's processor. Toeffect minimal involvement from the target device's processor in thedirect ‘PUT’ operation, the origin DMA engine transfers the data to bestored on the target device along with a specific identification of astorage location on the target device. The origin DMA knows the specificstorage location on the target device because the specific storagelocation for storing the data on the target device has been previouslyprovided by the target DMA engine to the origin DMA engine.

A remote ‘GET’ operation, sometimes denominated an ‘rGET,’ is anothermode of transmitting data from a DMA engine on an origin device to a DMAengine on a target device. A remote ‘GET’ operation allows data to betransmitted and stored on the target device with little involvement fromthe origin device's processor. To effect minimal involvement from theorigin device's processor in the remote ‘GET’ operation, the origin DMAengine stores the data in an storage location accessible by the targetDMA engine, notifies the target DMA engine, directly or out-of-bandthrough a shared memory transmission, of the storage location and thesize of the data ready to be transmitted, and the target DMA engineretrieves the data from storage location.

Monitoring data communications performance for a plurality of datacommunications modes may include monitoring a number of requests (168)in a message transmit request queue (162-165) for a data communicationslink (156). In the example of FIG. 2, each message transmit requestqueue (162-165) is associated with one particular data communicationslink (156). Each queue (162-165) includes entries for messages (170)that include data (176) to be transmitted by the communications adapters(160, 161) along a data communications link (156) associated with queue.

Monitoring data communications performance for a plurality of datacommunications modes may also include monitoring utilization of a sharedmemory space (158). In the example of FIG. 2, shared memory space (158)is allocated in RAM (140) of the accelerator. Utilization is theproportion of the allocated shared memory space to which data has beenstored for sending to a target device and has not yet been read orreceived by the target device, monitored by tracking the writes andreads to and from the allocated shared memory. In the hybrid computingenvironment (100) of FIG. 2, shared memory space, any memory in fact, islimited. As such, a shared memory space (158) may be filled duringexecution of an application program (166) such that transmission of datafrom the host computer (110) to an accelerator may be slowed, or evenstopped, due to space limitations in the shared memory space.

In some embodiments of the present invention, the hybrid computingenvironment (100) of FIG. 2 may be configured to operate as a parallelcomputing environment in which two or more instances the applicationprogram (166) executes on two or more host computers (110) in theparallel computing environment. In such embodiments, monitoring datacommunications performance across data communications modes may alsoinclude aggregating data communications performance information (174)across a plurality of instances of the application program (166)executing on two or more host computers in a parallel computingenvironment. The aggregated performance information (174) may be used tocalculate average communications latencies for data communicationsmodes, average number of requests in data communications links of aparticular fabric type, average shared memory utilization among theplurality of host computers and accelerators in the parallel computingenvironment, and so on as will occur to those of skill in the art. Anycombination of such measures may be used by the SLMPM for bothdetermining whether to transmit the data according to requested datacommunications mode and selecting another data communications mode fortransmitting the data if the data is not to be transmitted according tothe requested data communications mode.

The SLMPM (146) of FIG. 2 receives, from an application program (166) onthe host computer (110), a request (168) to transmit data (176)according to a data communications mode from the host computer (110) tothe accelerator (104). Such data (176) may include computer programinstructions compiled for execution by the accelerator (104), work piecedata for an application program executing on the accelerator (104), orsome combination of computer program instructions and work piece data.Receiving a request (168) to transmit data (176) according to a datacommunications mode may include receiving a request to transmit data bya specified fabric type, receiving a request to transmit data through aspecified data communications link from the host computer to theaccelerator, or receiving a request to transmit data from the hostcomputer to the accelerator according to a protocol.

A request (168) to transmit data (176) according to a datacommunications mode may be implemented as a user-level applicationfunction call through an API to the SLMPM (146), a call that expresslyspecifies a data communications mode according to protocol, fabric type,and link. A request implemented as a function call may specify aprotocol according to the operation of the function call itself. Adacs_put( ) function call, for example, may represent a call through anAPI exposed by an SLMPM implemented as a DACS library to transmit datain the default mode of a DMA ‘PUT’ operation. Such a call, from theperspective of the calling application and the programmer who wrote thecalling application, represents a request to the SLMPM library totransmit data according to the default mode, known to the programmer tobe default mode associated with the express API call. The calledfunction, in this example dacs_put( ), may be coded according toembodiments of the present invention, to make its own determinationwhether to transmit the data according to the requested datacommunications mode, that is, according to the default mode of thecalled function. In a further example, a dacs_send( ) instruction mayrepresent a call through an API exposed by an SLMPM implemented as aDACS library to transmit data in the default mode of an SMT ‘send’operation, where the called function dacs_send( ) is again codedaccording to embodiments of the present invention to make its owndetermination whether to transmit the data according to the requestedmode.

An identification of a particular accelerator in a function call mayeffectively specify a fabric type. Such a function call may include as acall parameters an identification of a particular accelerator. Anidentification of a particular accelerator by use of a PCIe ID, forexample, effectively specifies a PCI fabric type. In another, similar,example, an identification of a particular accelerator by use of a mediaaccess control (‘MAC’) address of an Ethernet adapter effectivelyspecifies the Ethernet fabric type. Instead of implementing theaccelerator ID of the function call from an application executing on thehost in such a way as to specify a fabric type, the function call mayonly include a globally unique identification of the particularaccelerator as a parameter of the call, thereby specifying only a linkfrom the host computer to the accelerator, not a fabric type. In thiscase, the function called may implement a default fabric type for usewith a particular protocol. If the function called in the SLMPM isconfigured with PCIe as a default fabric type for use with the DMAprotocol, for example, and the SLMPM receives a request to transmit datato the accelerator (104) according to the DMA protocol, a DMA PUT or DMAremote GET operation, the function called explicitly specifies thedefault fabric type for DMA, the PCIe fabric type.

In hybrid computing environments in which only one link of each fabrictype adapts a single host computer to a single accelerator, theidentification of a particular accelerator in a parameter of a functioncall, may also effectively specify a link. In hybrid computingenvironments where more than one link of each fabric type adapts a hostcomputer and an accelerator, such as two PCIe links connecting the hostcomputer (110) to the accelerator (104), the SLMPM function called mayimplement a default link for the accelerator identified in the parameterof the function call for the fabric type specified by the identificationof the accelerator.

The SLMPM (146) in the example of FIG. 2 also determines, in dependenceupon the monitored performance (174), whether to transmit the data (176)according to the requested data communications mode. Determining whetherto transmit the data (176) according to the requested datacommunications mode may include determining whether to transmit data bya requested fabric type, whether to transmit data through a requesteddata communications link, or whether to transmit data according to arequested protocol.

In hybrid computing environments according to embodiments of the presentinvention, where monitoring data communications performance across datacommunications modes includes monitoring a number of requests in amessage transmit request queue (162-165) for a data communications link,determining whether to transmit the data (176) according to therequested data communications mode may be carried out by determiningwhether the number of requests in the message transmit request queueexceeds a predetermined threshold. In hybrid computing environmentsaccording to embodiments of the present invention, where monitoring datacommunications performance for a plurality of data communications modesincludes monitoring utilization of a shared memory space, determiningwhether to transmit the data (176) according to the requested datacommunications mode may be carried out by determining whether theutilization of the shared memory space exceeds a predeterminedthreshold.

If the data is not to be transmitted according to the requested datacommunications mode, the SLMPM (146) selects, in dependence upon themonitored performance, another data communications mode for transmittingthe data and transmits the data (176) according to the selected datacommunications mode. Selecting another data communications mode fortransmitting the data may include selecting, in dependence upon themonitored performance, another data communications fabric type by whichto transmit the data, selecting a data communications link through whichto transmit the data, and selecting another data communicationsprotocol. Consider as an example, that the requested data communicationsmode is a DMA transmission using a PUT operation through link (138) ofthe PCIe fabric (130) to the accelerator (104). If the monitored dataperformance (174) indicates that the number of requests in transmitmessage request queue (162) associated with the link (138) exceeds apredetermined threshold, the SLMPM may select another fabric type, theEthernet fabric (128), and link (131, 132) through which to transmit thedata (176). Also consider that the monitored performance (176) indicatesthat current utilization of the shared memory space (158) is less than apredetermined threshold while the number of outstanding DMAtransmissions in the queue (162) exceeds a predetermined threshold. Insuch a case, the SLMPM (146) may also select another protocol, such as ashared memory transfer, by which to transmit the data (174).

Selecting, by the SLMPM, another data communications mode fortransmitting the data (172) may also include selecting a datacommunications protocol (178) in dependence upon data communicationsmessage size (172). Selecting a data communications protocol (178) independence upon data communications message size (172) may be carriedout by determining whether a size of a message exceeds a predeterminedthreshold. For larger messages (170), the DMA protocol may be apreferred protocol as processor utilization in making a DMA transfer ofa larger message (170) is typically less than the processor utilizationin making a shared memory transfer of a message of the same size.

As mentioned above, the SLMPM may also transmit the data according tothe selected data communications mode. Transmit the data according tothe selected data communications mode may include transmitting the databy the selected data communications fabric type, transmitting the datathrough the selected data communications link, or transmitting the dataaccording to the selected protocol. The SLMPM (146) may effect atransmission of the data according to the selected data communicationsmode by instructing, through a device driver, the communications adapterfor the data communications fabric type of the selected datacommunications mode to transmit the message (170) according to aprotocol of the selected data communications mode, where the messageincludes in a message header, an identification of the accelerator, andin the message payload, the data (176) to be transmitted.

For further explanation, FIG. 3 sets forth a block diagram of a furtherexemplary hybrid computing environment (100) useful for data processingaccording to embodiments of the present invention. The hybrid computingenvironment of FIG. 3 is similar the hybrid computing environment ofFIG. 2, including as it does, four compute nodes (102, 103), each ofwhich includes a host computer (110) having a host computer architectureand an accelerator (104) having an accelerator architecture where theaccelerator architecture is optimized, with respect to the host computerarchitecture, for speed of execution of a particular class of computingfunctions. The host computer (110) and the accelerator (104) are adaptedto one another for data communications by a system level message passingmodule (146) and two or more data communications fabrics (128, 130) ofat least two different fabric types. In the example of FIG. 3, the hostcomputer (110) is adapted to accelerator (104) by an Ethernet fabric(128) and a PCIe fabric (130).

The host computer (110) as illustrated in the expanded view of thecompute node (103) includes an x86 processor. An x86 processor is aprocessor whose architecture is based upon the architectural registerset of the Intel x86 series of microprocessors, the 386, the 486, the586 or Pentium™, and so on. Examples of x86 processors include theAdvanced Micro Devices (‘AMD’) Opteron™, the AMD Phenom™, the AMD AthlonXP™, the AMD Athlon 64™, Intel Nehalam™, Intel Pentium 4, Intel Core 2Duo, Intel Atom, and so on as will occur to those of skill in the art.The x86 processor (152) in the example of Figure illustrates a set of atypical architectural registers (154) found in many x86 processorsincluding, for example, an accumulator register (‘AX’), a base register(‘BX’), a counter register (‘CX’), a data register (‘DX’), a sourceindex register for string operations (‘SI’), a destination index forstring operations (‘DI’), a stack pointer (‘SP’), a stack base pointerfor holding the address of the current stack frame (‘BP’), and aninstruction pointer that holds the current instruction address (‘IP’).

The accelerator (104) in the example of FIG. 3 is illustrated as a CellBroadband Engine (‘CBE’) having a Cell Broadband Engine Architecture(‘CBEA’). A CBEA is a microprocessor architecture jointly developed bySony Computer Entertainment, Toshiba, and IBM, an alliance known as“STI.” Microprocessors implemented according to the CBEA are sometimesreferred to as ‘Cell’ processors or simply as CBEs. The CBEA combines ageneral-purpose POWER architecture core, a Power Processing Element(‘PPE’) (148), of modest performance with streamlined co-processingelements, called Synergistic Processing Elements (‘SPEs’) (308) whichgreatly accelerate multimedia and vector processing applications, aswell as many other forms of dedicated computation. The CBE architectureemphasizes efficiency/watt, prioritizes bandwidth over latency, andfavors peak computational throughput over simplicity of program code.

The accelerator (104) of FIG. 3, implemented as a CBE, includes a mainprocessor (148) that in this example is a Power Processing Element(‘PPE’), eight fully-functional co-processors called SPEs (308), and ahigh-bandwidth circular data bus connecting the PPE and the SPEs, calledthe Element Interconnect Bus (‘EIB’) (312). The PPE (148) is a POWERarchitecture processor with a two-way multithreaded core acting as acontroller for the eight SPEs (308). The term “POWER architecture” hererefers to IBM's different generations of processor architectures, abroad term including all products based on POWER, PowerPC and Cellarchitectures. The architectural registers (150) of the PPE (148) of theCBE accelerator (104) therefore are different from those of the x86processor (152) of the host computer (110). The PPE (148) of FIG. 3includes an example set of architectural registers (150) of the POWERarchitecture, including 32 general purpose registers (‘GPRs’), 32floating point registers (‘FPRs’), a fixed-point exception register(‘XER’), a count register (‘CTR’), a Condition register (‘CR’), aninstruction address register (‘IAR’), a link register (‘LR’), and aprocessor version register (‘PVR’).

The SPEs (308) handle most of the computational workload of the CBE(104). While the SPEs are optimized for vectorized floating point codeexecution, the SPEs also may execute operating systems, such as, forexample, a lightweight, modified version of Linux with the operatingsystem stored in local memory (141) on the SPE. Each SPE (308) in theexample of FIG. 3 includes a Synergistic Processing Unit (‘SPU’) (302),and a Memory Flow Controller (‘MFC’) (310). An SPU (302) is a ReducedInstruction Set Computing (‘RISC’) processor with 128-bit singleinstruction, multiple data (‘SIMD’) organization for single and doubleprecision instructions. In some implementations, an SPU may contain a256 KB embedded Static RAM (141) for instructions and data, called localstorage which is visible to the PPE (148) and can be addressed directlyby software. Each SPU (302) can support up to 4 Gigabyte (‘GB’) of localstore memory. The local store does not operate like a conventional CPUcache because the local store is neither transparent to software nordoes it contain hardware structures that predict which data to load. TheSPUs (302) also implement architectural registers (306) different fromthose of the PPE which include a 128-bit, 128-entry register file (307).An SPU (302) can operate on 16 8-bit integers, 8 16-bit integers, 432-bit integers, or 4 single precision floating-point numbers in asingle clock cycle, as well as execute a memory operation.

The MFC (310) integrates the SPUs (302) in the CBE (104). The MFC (310)provides an SPU with data transfer and synchronization capabilities, andimplements the SPU interface to the EIB (312) which serves as thetransportation hub for the CBE (104). The MFC (310) also implements thecommunication interface between the SPE (308) and PPE (148), and servesas a data transfer engine that performs bulk data transfers between thelocal storage (141) of an SPU (302) and CBE system memory, RAM (140),through DMA. By offloading data transfer from the SPUs (302) ontodedicated data transfer engines, data processing and data transferproceeds in parallel, supporting advanced programming methods such assoftware pipelining and double buffering. Providing the ability toperform high performance data transfer asynchronously and in parallelwith data processing on the PPE (148) and SPEs (302), the MFC (310)eliminates the need to explicitly interleave data processing andtransfer at the application level.

The SLMPM (146) in the example of FIG. 3 processes data in the hybridcomputing environment (100) according to embodiments of the presentinvention by monitoring data communications performance for a pluralityof data communications modes between the host computer (110) and theaccelerator (104); receiving, from an application program (166) on thehost computer (110), a request to transmit data according to a datacommunications mode from the host computer (110) to the accelerator(104); determining, in dependence upon the monitored performance,whether to transmit the data according to the requested datacommunications mode; and if the data is not to be transmitted accordingto the requested data communications mode: selecting, in dependence uponthe monitored performance, another data communications mode fortransmitting the data and transmitting the data according to theselected data communications mode.

For further explanation, FIG. 4 sets forth a block diagram of a furtherexemplary hybrid computing environment (100) useful for data processingaccording to embodiments of the present invention. The hybrid computingenvironment of FIG. 4 is similar the hybrid computing environment ofFIG. 2, including as it does, four compute nodes (102, 103), each ofwhich includes a host computer (110) having a host computer architectureand one or more accelerators (104) each having an acceleratorarchitecture where the accelerator architecture is optimized, withrespect to the host computer architecture, for speed of execution of aparticular class of computing functions. The host computer (110) and theaccelerator (104) in the example of FIG. 4 are adapted to one anotherfor data communications by a system level message passing module (146)and two or more data communications fabrics (128, 130) of at least twodifferent fabric types. In the example of FIG. 4, the host computer(110) is adapted to accelerator (104) by an Ethernet fabric (128) and aPCIe fabric (130).

FIG. 4 illustrates an example of a hybrid computing environment similarto that implemented in the LANL supercomputer. The host computer (110),as illustrated by the expanded view of the compute node (103),implemented in the LANL supercomputer includes two AMD Opteronprocessors (155), each of which is a dual-core processor. Each of thecores (152) of the host computer (110) is illustrated in the example ofFIG. 4 as a single, fully functional x86 processor core with each corehaving its own set of architectural registers (154). Each of theprocessor cores (152) in the example of FIG. 4 is operatively coupled toRAM (142) where an instance of an application program (166), an instanceof the SLMPM (146), and an operating system (145) is stored. In theexample of the LANL supercomputer, the SLMPM (146) is the DataCommunication and Synchronization (‘DACS’) library improved according toembodiments of the present invention.

Each x86 processor core (152) in the example of FIG. 4 is adaptedthrough an Ethernet (128) and PCIe (130) fabric to a separateaccelerator (104) implemented as a CBE as described above with respectto FIG. 3. Each core (152) of each AMD Opteron processor (155) in thehost computer (110) in this example is connected to at least one CBE.Although in this example the ratio of cores of the Opteron processors toCBEs (104) is one-to-one, readers of skill in the art will recognizethat other example embodiments may implement different ratios ofprocessor cores to accelerators such as, for example, one-to-two,one-to-three, and so on.

Each instance of the SLMPM (146) executing on each x86 processor core(152) in the example of FIG. 4 processes data in the hybrid computingenvironment (100) according to embodiments of the present invention bymonitoring data communications performance across data communicationsmodes between the host computer (110) and the accelerator (104)connected to the processor core (152); receiving, from the instance ofthe application program (166) executing on the processor core (152) ofthe host computer (110), a request to transmit data according to a datacommunications mode from the host computer (110) to the accelerator(104) connected to the processor core (152); determining, in dependenceupon the monitored performance, whether to transmit the data accordingto the requested data communications mode; and if the data is not to betransmitted according to the requested data communications mode:selecting, in dependence upon the monitored performance, another datacommunications mode for transmitting the data and transmitting the dataaccording to the selected data communications mode.

For further explanation, FIG. 5 sets forth a flow chart illustrating anexemplary method for data processing in a hybrid computing environmentaccording to embodiments of the present invention. The method of FIG. 5is carried out in a hybrid computing environment similar to the hybridcomputing environments described above in this specification. Such ahybrid computing environment includes a host computer (110 on FIG. 2)having a host computer architecture and an accelerator (104 on FIG. 2)having an accelerator architecture, the accelerator architectureoptimized, with respect to the host computer architecture, for speed ofexecution of a particular class of computing functions, the hostcomputer (110 on FIG. 2) and the accelerator (104 on FIG. 2) adapted toone another for data communications by an SLMPM (146 on FIG. 2) and bytwo or more data communications fabrics (128, 130 on FIG. 2) of at leasttwo different fabric types.

The method of FIG. 5 includes monitoring (504), by the system levelmessage passing module, data communications performance across datacommunications modes between the host computer and the accelerator. Adata communications mode is a combination of a data communicationsfabric type, a data communications link, and a data communicationsprotocol. The method of FIG. 5 also includes receiving (508), by thesystem level message passing module from an application program (166) onthe host computer, a request (168) to transmit data according to a datacommunications mode (502) from the host computer to the accelerator. Inthe method of FIG. 5, receiving (508) a request (168) to transmit dataaccording to a data communications mode (502) may include receiving(510) a request to transmit data by a specified fabric type, receiving(512) a request to transmit data through a specified data communicationslink from the host computer to the accelerator, or receiving (514) arequest to transmit data from the host computer to the acceleratoraccording to a protocol.

The method of FIG. 5 also includes determining (516), by the SLMPM, independence upon the monitored performance (506) whether to transmit thedata according to the requested data communications mode (502).Determining (516), by the SLMPM, in dependence upon the monitoredperformance (506) whether to transmit the data according to therequested data communications mode (502) may be carried out in variousways. In embodiments in which the SLMPM receives (510) a request totransmit data by a specified fabric type, determining (516) whether totransmit the data according to the requested data communications mode(502) may be carried out by determining (518) whether to transmit databy the requested fabric type. In embodiments in which the SLMPM receives(512) a request to transmit data through a specified link, determining(516) whether to transmit the data according to the requested datacommunications mode (502) may be carried out by determining (520)whether to transmit the data through the requested data communicationslink. And in embodiments in which the SLMPM receives (514) a request totransmit data according to a protocol, determining (516) whether totransmit the data according to the requested data communications mode(502) may be carried out by determining (522) whether to transmit thedata according to the requested protocol.

If the SLMPM makes a determination to transmit the data according to therequested fabric type and to transmit the data through the requestedlink and to transmit the data according to the requested protocol, sucha combination of determinations is a determination (519) to transmit thedata according to the requested protocol. If the SLMPM makes such adetermination (519) to transmit the data according to the requestedprotocol, the method of FIG. 5 continues by transmitting (524) the dataaccording to the requested data communications mode. In the method ofFIG. 5, the SLMPM may make a determination not (521) to transmit thedata by the requested fabric type, not (523) to transmit data throughthe requested data communications link, or not (525) to transmit thedata according to the requested protocol, any of which also represents adetermination not (517) to transmit the data according to a requesteddata communications mode. That is any determination not to transmit thedata according to any one requested element of a data communicationsmode is also a determination not (517) to transmit the data according toa requested data communications mode.

If data is not (521, 523, 525, 517) to be transmitted according to therequested data communications mode, the method of FIG. 5 continues byselecting (526), by the SLMPM, in dependence upon the monitoredperformance (506) another data communications mode for transmitting thedata and transmitting (534) the data by the SLMPM according to theselected data communications mode. In the method of FIG. 5, selecting(526), by the system level message passing module, in dependence uponthe monitored performance another data communications mode fortransmitting the data may be carried out in various ways. In embodimentsin which the SLMPM determines (518) not to transmit data by therequested fabric type (521), selecting (526), by the system levelmessage passing module, in dependence upon the monitored performanceanother data communications mode for transmitting the data may becarried out by selecting (528) in dependence upon the monitoredperformance (506) another data communications fabric type by which totransmit the data. In embodiments in which the SLMPM determines (520)not to transmit the data through the requested data communications link(523), selecting (526), by the system level message passing module, independence upon the monitored performance another data communicationsmode for transmitting the data may be carried out by selecting (530) independence upon the monitored performance (506) a data communicationslink through which to transmit the data. And in embodiments in which theSLMPM determines (522) not to transmit the data according to therequested protocol (525), selecting (526), by the system level messagepassing module, in dependence upon the monitored performance anotherdata communications mode for transmitting the data may be carried out byselecting (532) in dependence upon the monitored performance (506)another data communications protocol.

In the method of FIG. 5, transmitting (534) the data according to theselected data communications mode may also be carried out in variousways. In embodiments in which the SLMPM selects (528) another datacommunications fabric type by which to transmit the data, transmitting(534) the data according to the selected data communications mode may becarried out by transmitting (536) the data by the selected datacommunications fabric type. In embodiments in which the SLMPM selects(530) a data communications link through which to transmit the data,transmitting (534) the data according to the selected datacommunications mode may be carried out by transmitting (538) the datathrough the selected data communications link. And in embodiments inwhich the SLMPM selects (532) another data communications protocol,transmitting (534) the data according to the selected datacommunications mode may be carried out by transmitting (540) the dataaccording to the selected protocol.

For further explanation, FIG. 6 sets forth a flow chart illustrating afurther exemplary method for data processing in a hybrid computingenvironment according to embodiments of the present invention. Themethod of FIG. 6, like the method of FIG. 5 is carried out in a hybridcomputing environment similar to the hybrid computing environmentsdescribed above in this specification. Such a hybrid computingenvironment includes a host computer (110 on FIG. 2) having a hostcomputer architecture and an accelerator (104 on FIG. 2) having anaccelerator architecture, the accelerator architecture optimized, withrespect to the host computer architecture, for speed of execution of aparticular class of computing functions, the host computer (110 on FIG.2) and the accelerator (104 on FIG. 2) adapted to one another for datacommunications by a system level message passing module (146 on FIG. 2)and by two or more data communications fabrics (128, 130 on FIG. 2) ofat least two different fabric types. The method of FIG. 6 is similar tothe method of FIG. 5 including, as it does, the system level messagepassing module's monitoring (504) data communications performance for aplurality of data communications modes between the host computer and theaccelerator; receiving (508), from an application program on the hostcomputer, a request to transmit data according to a data communicationsmode from the host computer to the accelerator; determining (516), independence upon the monitored performance, whether to transmit the dataaccording to the requested data communications mode; and if the data isnot to be transmitted according to the requested data communicationsmode: selecting (526), in dependence upon the monitored performance,another data communications mode for transmitting the data andtransmitting (534) the data according to the selected datacommunications mode. The method of FIG. 6 differs from the method ofFIG. 5, however, in that in the method of FIG. 6, monitoring (504) datacommunications performance for a plurality of data communications modesbetween the host computer and the accelerator includes monitoring anumber (606) of requests (168) in a message transmit request queue (602)for a data communications link. Also in the method of FIG. 6,determining (516) whether to transmit the data according to therequested data communications mode includes determining (610) whetherthe number (606) of requests (168) in the message transmit request queue(602) exceeds a predetermined threshold (608). The predeterminedthreshold (608) may be implemented as a user-configurable value, a valuethat is modified dynamically throughout operation of the hybridcomputing environment, a static value, or in other ways as will occur tothose of skill in the art.

For further explanation, FIG. 7 sets forth a flow chart illustrating afurther exemplary method for data processing in a hybrid computingenvironment according to embodiments of the present invention. Themethod of FIG. 7, like the method of FIG. 5, is carried out in a hybridcomputing environment similar to the hybrid computing environmentsdescribed above in this specification. Such a hybrid computingenvironment includes a host computer (110 on FIG. 2) having a hostcomputer architecture and an accelerator (104 on FIG. 2) having anaccelerator architecture, the accelerator architecture optimized, withrespect to the host computer architecture, for speed of execution of aparticular class of computing functions, the host computer (110 on FIG.2) and the accelerator (104 on FIG. 2) adapted to one another for datacommunications by a system level message passing module (146 on FIG. 2)and by two or more data communications fabrics (128, 130 on FIG. 2) ofat least two different fabric types. The method of FIG. 7 is similar tothe method of FIG. 5 including, as it does, the system level messagepassing module's monitoring (504) data communications performance for aplurality of data communications modes between the host computer and theaccelerator; receiving (508), from an application program on the hostcomputer, a request to transmit data according to a data communicationsmode from the host computer to the accelerator; determining (516), independence upon the monitored performance, whether to transmit the dataaccording to the requested data communications mode; and if the data isnot to be transmitted according to the requested data communicationsmode: selecting (526), in dependence upon the monitored performance,another data communications mode for transmitting the data andtransmitting (534) the data according to the selected datacommunications mode. The method of FIG. 7 differs from the method ofFIG. 5, however, in that in the method of FIG. 7, monitoring (504) datacommunications performance for a plurality of data communications modesbetween the host computer and the accelerator includes monitoringutilization (704) of a shared memory space. Also in the method of FIG.7, determining (516) whether to transmit the data according to therequested data communications mode includes determining (708) whetherthe utilization (704) of the shared memory space exceeds a predeterminedthreshold (706). The predetermined threshold (706) may be implemented asa user-configurable value, a value that is modified dynamicallythroughout operation of the hybrid computing environment, a staticvalue, or in other ways as will occur to those of skill in the art.

For further explanation, FIG. 8 sets forth a flow chart illustrating afurther exemplary method for data processing in a hybrid computingenvironment according to embodiments of the present invention. Themethod of FIG. 8, like the method of FIG. 5, is carried out in a hybridcomputing environment similar to the hybrid computing environmentsdescribed above in this specification. Such a hybrid computingenvironment includes a host computer (110 on FIG. 2) having a hostcomputer architecture and an accelerator (104 on FIG. 2) having anaccelerator architecture, the accelerator architecture optimized, withrespect to the host computer architecture, for speed of execution of aparticular class of computing functions, the host computer (110 on FIG.2) and the accelerator (104 on FIG. 2) adapted to one another for datacommunications by a system level message passing module (146 on FIG. 2)and by two or more data communications fabrics (128, 130 on FIG. 2) ofat least two different fabric types. The method of FIG. 8 is similar tothe method of FIG. 5 including, as it does, the system level messagepassing module's monitoring (504) data communications performance for aplurality of data communications modes between the host computer and theaccelerator; receiving (508), from an application program on the hostcomputer, a request to transmit data according to a data communicationsmode from the host computer to the accelerator; determining (516), independence upon the monitored performance, whether to transmit the dataaccording to the requested data communications mode; and if the data isnot to be transmitted according to the requested data communicationsmode: selecting (526), in dependence upon the monitored performance,another data communications mode for transmitting the data andtransmitting (534) the data according to the selected datacommunications mode. The method of FIG. 8 differs from the method ofFIG. 5, however, in that in the method of FIG. 8, monitoring (504) datacommunications performance for a plurality of data communications modesbetween the host computer and the accelerator includes aggregating (802)data communications performance information (804) across a plurality ofinstances of the application program executing on a plurality of hostcomputers in a parallel computing environment. Also in the method ofFIG. 8, selecting (526), in dependence upon the monitored performance,another data communications mode for transmitting the data includesselecting (808) a data communications protocol in dependence upon datacommunications message size (806).

Exemplary embodiments of the present invention are described largely inthe context of data processing in a fully functional hybrid computingenvironment. Readers of skill in the art will recognize, however, thatmethod aspects of the present invention also may be embodied in acomputer program product disposed on signal bearing media for use withany suitable data processing system. Such signal bearing media may betransmission media or recordable media for machine-readable information,including magnetic media, optical media, or other suitable media.Examples of recordable media include magnetic disks in hard drives ordiskettes, compact disks for optical drives, magnetic tape, and othersas will occur to those of skill in the art. Examples of transmissionmedia include telephone networks for voice communications and digitaldata communications networks such as, for example, Ethernets™ andnetworks that communicate with the Internet Protocol and the World WideWeb. Persons skilled in the art will immediately recognize that anycomputer system having suitable programming means will be capable ofexecuting the steps of the method of the invention as embodied in aprogram product. Persons skilled in the art will recognize immediatelythat, although some of the exemplary embodiments described in thisspecification are oriented to software installed and executing oncomputer hardware, nevertheless, alternative embodiments implemented asfirmware or as hardware are well within the scope of the presentinvention.

It will be understood from the foregoing description that modificationsand changes may be made in various embodiments of the present inventionwithout departing from its true spirit. The descriptions in thisspecification are for purposes of illustration only and are not to beconstrued in a limiting sense. The scope of the present invention islimited only by the language of the following claims.

1. A method of data processing in a hybrid computing environment, thehybrid computing environment comprising: a host computer having a hostcomputer architecture; an accelerator having an acceleratorarchitecture, the accelerator architecture optimized, with respect tothe host computer architecture, for speed of execution of a particularclass of computing functions; the host computer and the acceleratoradapted to one another for data communications by a system level messagepassing module; the host computer and the accelerator adapted to oneanother for data communications by two or more data communicationsfabrics of at least two different fabric types; the method comprising:monitoring, by the system level message passing module, datacommunications performance for a plurality of data communications modesbetween the host computer and the accelerator; receiving, by the systemlevel message passing module from an application program on the hostcomputer, a request to transmit data according to a data communicationsmode from the host computer to the accelerator; determining, by thesystem level message passing module, in dependence upon the monitoredperformance whether to transmit the data according to the requested datacommunications mode; and if the data is not to be transmitted accordingto the requested data communications mode: selecting, by the systemlevel message passing module, in dependence upon the monitoredperformance another data communications mode for transmitting the dataand transmitting the data by the system level message passing moduleaccording to the selected data communications mode.
 2. The method ofclaim 1 wherein each data communications mode comprises a datacommunications fabric type, a data communications link, and a datacommunications protocol.
 3. The method of claim 1 wherein: receiving arequest to transmit data according to a data communications mode furthercomprises receiving a request to transmit data by a specified fabrictype; determining whether to transmit the data according to therequested data communications mode further comprises determining whetherto transmit data by the requested fabric type; selecting another datacommunications mode for transmitting the data further comprisesselecting in dependence upon the monitored performance another datacommunications fabric type by which to transmit the data; andtransmitting the data according to the selected data communications modefurther comprises transmitting the data by the selected datacommunications fabric type.
 4. The method of claim 1 wherein: receivinga request to transmit data according to a data communications modefurther comprises receiving a request to transmit data through aspecified data communications link from the host computer to theaccelerator; determining whether to transmit the data according to therequested data communications mode further comprises determining whetherto transmit the data through the requested data communications link;selecting another data communications mode for transmitting the datafurther comprises selecting in dependence upon the monitored performancea data communications link through which to transmit the data; andtransmitting the data according to the selected data communications modefurther comprises transmitting the data through the selected datacommunications link.
 5. The method of claim 1 wherein: receiving arequest to transmit data according to a data communications mode furthercomprises receiving a request to transmit data from the host computer tothe accelerator according to a protocol; determining whether to transmitthe data according to the requested data communications mode furthercomprises determining whether to transmit the data according to therequested protocol; selecting another data communications mode fortransmitting the data further comprises selecting in dependence upon themonitored performance another data communications protocol; andtransmitting the data according to the selected data communications modefurther comprises transmitting the data according to the selectedprotocol.
 6. The method of claim 1 wherein: monitoring datacommunications performance for a plurality of data communications modesfurther comprises monitoring a number of requests in a message transmitrequest queue for a data communications link; and determining whether totransmit the data according to the requested data communications modefurther comprises determining whether the number of requests in themessage transmit request queue exceeds a predetermined threshold.
 7. Themethod of claim 1 wherein: monitoring data communications performancefor a plurality of data communications modes further comprisesmonitoring utilization of a shared memory space; and determining whetherto transmit the data according to the requested data communications modefurther comprises determining whether the utilization of the sharedmemory space exceeds a predetermined threshold.
 8. The method of claim 1wherein: monitoring data communications performance for a plurality ofdata communications modes further comprises aggregating datacommunications performance information across a plurality of instancesof the application program executing on a plurality of host computers ina parallel computing environment.
 9. The method of claim 1 whereinselecting another data communications mode for transmitting the datafurther comprises selecting a data communications protocol in dependenceupon data communications message size.
 10. A hybrid computingenvironment comprising: a host computer having a host computerarchitecture; an accelerator having an accelerator architecture, theaccelerator architecture optimized, with respect to the host computerarchitecture, for speed of execution of a particular class of computingfunctions; the host computer and the accelerator adapted to one anotherfor data communications by a system level message passing module; thehost computer and the accelerator adapted to one another for datacommunications by two or more data communications fabrics of at leasttwo different fabric types; the system level message passing modulecomprising computer program instructions capable of: monitoring datacommunications performance for a plurality of data communications modesbetween the host computer and the accelerator; receiving, from anapplication program on the host computer, a request to transmit dataaccording to a data communications mode from the host computer to theaccelerator; determining, in dependence upon the monitored performance,whether to transmit the data according to the requested datacommunications mode; and if the data is not to be transmitted accordingto the requested data communications mode: selecting, in dependence uponthe monitored performance, another data communications mode fortransmitting the data and transmitting the data according to theselected data communications mode.
 11. The hybrid computing environmentof claim 10 wherein each data communications mode comprises a datacommunications fabric type, a data communications link, and a datacommunications protocol.
 12. The hybrid computing environment of claim10 wherein: receiving a request to transmit data according to a datacommunications mode further comprises receiving a request to transmitdata by a specified fabric type; determining whether to transmit thedata according to the requested data communications mode furthercomprises determining whether to transmit data by the requested fabrictype; selecting another data communications mode for transmitting thedata further comprises selecting in dependence upon the monitoredperformance another data communications fabric type by which to transmitthe data; and transmitting the data according to the selected datacommunications mode further comprises transmitting the data by theselected data communications fabric type.
 13. The hybrid computingenvironment of claim 10 wherein: receiving a request to transmit dataaccording to a data communications mode further comprises receiving arequest to transmit data through a specified data communications linkfrom the host computer to the accelerator; determining whether totransmit the data according to the requested data communications modefurther comprises determining whether to transmit the data through therequested data communications link; selecting another datacommunications mode for transmitting the data further comprisesselecting in dependence upon the monitored performance a datacommunications link through which to transmit the data; and transmittingthe data according to the selected data communications mode furthercomprises transmitting the data through the selected data communicationslink.
 14. The hybrid computing environment of claim 10 wherein:receiving a request to transmit data according to a data communicationsmode further comprises receiving a request to transmit data from thehost computer to the accelerator according to a protocol; determiningwhether to transmit the data according to the requested datacommunications mode further comprises determining whether to transmitthe data according to the requested protocol; selecting another datacommunications mode for transmitting the data further comprisesselecting in dependence upon the monitored performance another datacommunications protocol; and transmitting the data according to theselected data communications mode further comprises transmitting thedata according to the selected protocol.
 15. The hybrid computingenvironment of claim 10 wherein: monitoring data communicationsperformance for a plurality of data communications modes furthercomprises monitoring a number of requests in a message transmit requestqueue for a data communications link; and determining whether totransmit the data according to the requested data communications modefurther comprises determining whether the number of requests in themessage transmit request queue exceeds a predetermined threshold. 16.The hybrid computing environment of claim 10 wherein: monitoring datacommunications performance for a plurality of data communications modesfurther comprises monitoring utilization of a shared memory space; anddetermining whether to transmit the data according to the requested datacommunications mode further comprises determining whether theutilization of the shared memory space exceeds a predeterminedthreshold.
 17. The hybrid computing environment of claim 10 wherein:monitoring data communications performance for a plurality of datacommunications modes further comprises aggregating data communicationsperformance information across a plurality of instances of theapplication program executing on a plurality of host computers in aparallel computing environment.
 18. The hybrid computing environment ofclaim 10 wherein selecting another data communications mode fortransmitting the data further comprises selecting a data communicationsprotocol in dependence upon data communications message size.
 19. Acomputer program product for data processing in a hybrid computingenvironment, the hybrid computing environment comprising: a hostcomputer having a host computer architecture; an accelerator having anaccelerator architecture, the accelerator architecture optimized, withrespect to the host computer architecture, for speed of execution of aparticular class of computing functions; the host computer and theaccelerator adapted to one another for data communications by a systemlevel message passing module; the host computer and the acceleratoradapted to one another for data communications by two or more datacommunications fabrics of at least two different fabric types; thecomputer program product disposed in a computer readable, signal bearingmedium, the computer program product comprising computer programinstructions capable of: monitoring, by the system level message passingmodule, data communications performance for a plurality of datacommunications modes between the host computer and the accelerator;receiving, by the system level message passing module from anapplication program on the host computer, a request to transmit dataaccording to a data communications mode from the host computer to theaccelerator; determining, by the system level message passing module, independence upon the monitored performance whether to transmit the dataaccording to the requested data communications mode; and if the data isnot to be transmitted according to the requested data communicationsmode: selecting, by the system level message passing module, independence upon the monitored performance another data communicationsmode for transmitting the data and transmitting the data by the systemlevel message passing module according to the selected datacommunications mode.
 20. The computer program product of claim 19wherein each data communications mode comprises a data communicationsfabric type, a data communications link, and a data communicationsprotocol.
 21. The computer program product of claim 19 wherein:receiving a request to transmit data according to a data communicationsmode further comprises receiving a request to transmit data by aspecified fabric type; determining whether to transmit the dataaccording to the requested data communications mode further comprisesdetermining whether to transmit data by the requested fabric type;selecting another data communications mode for transmitting the datafurther comprises selecting in dependence upon the monitored performanceanother data communications fabric type by which to transmit the data;and transmitting the data according to the selected data communicationsmode further comprises transmitting the data by the selected datacommunications fabric type.
 22. The computer program product of claim 19wherein: receiving a request to transmit data according to a datacommunications mode further comprises receiving a request to transmitdata through a specified data communications link from the host computerto the accelerator; determining whether to transmit the data accordingto the requested data communications mode further comprises determiningwhether to transmit the data through the requested data communicationslink; selecting another data communications mode for transmitting thedata further comprises selecting in dependence upon the monitoredperformance a data communications link through which to transmit thedata; and transmitting the data according to the selected datacommunications mode further comprises transmitting the data through theselected data communications link.
 23. The computer program product ofclaim 19 wherein: receiving a request to transmit data according to adata communications mode further comprises receiving a request totransmit data from the host computer to the accelerator according to aprotocol; determining whether to transmit the data according to therequested data communications mode further comprises determining whetherto transmit the data according to the requested protocol; selectinganother data communications mode for transmitting the data furthercomprises selecting in dependence upon the monitored performance anotherdata communications protocol; and transmitting the data according to theselected data communications mode further comprises transmitting thedata according to the selected protocol.
 24. The computer programproduct of claim 19 wherein: monitoring data communications performancefor a plurality of data communications modes further comprisesmonitoring a number of requests in a message transmit request queue fora data communications link; and determining whether to transmit the dataaccording to the requested data communications mode further comprisesdetermining whether the number of requests in the message transmitrequest queue exceeds a predetermined threshold.
 25. The computerprogram product of claim 19 wherein: monitoring data communicationsperformance for a plurality of data communications modes furthercomprises monitoring utilization of a shared memory space; anddetermining whether to transmit the data according to the requested datacommunications mode further comprises determining whether theutilization of the shared memory space exceeds a predeterminedthreshold.
 26. The computer program product of claim 19 wherein:monitoring data communications performance for a plurality of datacommunications modes further comprises aggregating data communicationsperformance information across a plurality of instances of theapplication program executing on a plurality of host computers in aparallel computing environment.
 27. The computer program product ofclaim 19 wherein selecting another data communications mode fortransmitting the data further comprises selecting a data communicationsprotocol in dependence upon data communications message size.